The Twenty-Fifth Last Chance
by Vilva
Summary: The Demon Guardian AU that nobody wanted! Join Dipper and Mabel as they bond with their guardians and learn stuff. Magical stuff. It's great. No ships as of yet! Sry not sry.
1. Prologue:

**A/N: Switching fandoms like no body's business! Yup, here it is! The Demon Guardian AU that NO one asked for! Ah well...**

 **Disclaimer: I didn't think up this AU and I certainly didn't think up Gravity Falls.**

 **Inspired By The Amazing:** **starfleetrambo . tumblr**

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Unseen birds, perched overhead on the great boughs of towering evergreens, called to one another in lilting voices. Mysterious creatures with glowing eyes darted through the shadows, the only sign of their presence being the occasional rustle in the thick vegetation. Sunlight shone in slivered rays, a few patches of filtered gold sneaking into the inky darkness of the forest.

It was a wild and untamed place with a magic of its own.

In this eerie forest, sat a boy who looked distinctively out of place wearing a worn baseball cap bearing faded blue pine tree perched dangerously upon brown hair that was clustered in thick curls. His scrawny frame was hidden with a puffy vest, dotted by mysterious stains. With the addition of his comically reddened nose, the boy had the certain air of an inexperienced, city-raised, Boy Scout who has gone off trail. His knobby, scabbed knees and elbows (littered with bug bites) did nothing to help.

However, if one bothered to look carefully, they would see something quite different. They would notice the calluses on his fingers. They would notice the beginnings of lean muscle clinging to his bony legs. They would see white remains of scars lacing his tanned hands and others twisting into the sleeves of his tee-shirt. They would notice the respectful distance the strange shadows kept. They would see, behind the wisdom and experience, an otherworldly glint.

Yes. Even if he didn't know it, Dipper Pines had earned his place in the forest.

* * *

Dipper frowned at the messily scribbled and smeared seal before tearing it out of his sketchbook and wadding it up. Frustrated, he tossed it as far as he could. It soared feebly towards the earth before a small breeze picked it up and deposited on the ground, joining the numerous paper wads. Dipper's face flushed an interesting shade of red before he aggressively turned away, pulling out a fresh pencil (the other, littered with bite marks, was beyond rescue). The sound of intense scribbling filled the forest before another paper wad joined its predecessors.

"No, no, no, no!"

The boy continued to sketch, occasionally muttering 'No, no that symbol goes here', accompanied by frustrated erasing that almost wore a hole in the paper. Whenever he snapped his pencil lead, Dipper pulled out a pencil sharpener, and hastily murdered the pencil tip. Page after page of complex diagrams and signets were crumpled and tossed.

The sun began to set, turning the sky a bright orange. The shadows grew longer, the wind colder and more biting. Still Dipper continued to scribble with a frantic concentration, never tearing his gaze away from the sketchpad.

Pencil after pencil was reduced to stubs, and quite a few crushed to splinters by his nervous gnawing.

 _If Mercury is positioned here, then shouldn't Sulfur be directly across it?_ Dipper chewed thoughtfully. _Wait, wait, do you have to put Salt before or after? I mean, I already have **two** filtration signs, but….oh man I probably need another one don't I? Stupid good-for-nothing brain!_

Frenzied erasing sounds.

 _…Wait. If I do add another one, then doesn't that push my cementation signs too far to the left? Ugh, I'm getting nowhere! I could always just use the journal-_ His hand strayed toward his vest pocket but he snapped it back and clenched his fist. _No! I can't keep depending on it! Mabel did it by herself so I can too!_

Dipper let out a groan. What had Tad said? ' _There needs to be a perfect distance between the origin and the cementation. Otherwise they will overlap and you will have no base substance to work with'. Yep, another failure._

He ripped the wrinkled paper out with a sigh and tossed it. Dipper then returned to his drawing before realizing

 _I'm out of paper._

With a sigh, he threw away the doodle-covered, cardboard backing of what was left of his sketchpad. Dipper tossed a glance at the setting sun, rubbing his temples tiredly.

 _Great. I just demolished an entire sketchpad. And I'm **still** nowhere. _

He slouched over and buried his head in his hands, exhaling loudly. Dipper gave a sudden twitch and he ground his teeth. His brow furrowed and he let out irritated huff. At last, Dipper whirled around and snapped at a nearby shrub.

"I know you're there!"

The shrub didn't stir a leaf, irking the boy even more.

"Alright you can stop being cute! That stupid link works both ways you know!"

The bush cheerfully continued to do nothing. Already angered by his continuous failure, Dipper picked up the nearest pencil and flung it in the direction of the bush.

It was a weak throw but the bush was close enough to be within range. Just before the pencil hit the bush, a ripple in the air, similar to a heat wave, appeared and intercepted it. The pencil slowed until it was suspended in a faint, neon blue glow.

Suddenly, a spindly hand in tight black gloves stretched through the bushes leaves and neatly snatched up the pencil. Two spidery legs, both in yellow dress pants, slipped out fluidly, without so much as a whisper from the leaves. A long torso, clothed in a black dress-shirt, absolutely useless suspenders, and a bright yellow coat, sloppily hanging of his angular frame.

Bill Cipher stood there, a tall 'man' who definitely should not have been able to fit in a bush, his gold-bricked pyramid head that appeared to glow topped by a tall, black top hat. His one eye crinkled with mirth before he sweeps off his top hat in an over dramatic bow, twirling the pencil in his other hand.

Although his pyramid head should have unbalanced and sent him sprawling onto the ground, Bill immediately bounced up, with a flexibility rivaling Olympic gymnasts, his every move cartoonish and full of contained energy. Dipper merely scowled darkly at this display.

 _Show off,_ he thought, miffed at this casual display of magic. Magic _he_ should have been able to control just as easily. Aloud, Dipper said, "How long have you been here?"

The boy's bluntness only served to amuse the demon, who would probably be grinning his head off, if he had a mouth. He then smoothly pulled a gold cane from who-knows-where, settling his weight comfortably on it. _Like a cat,_ Dipper thought. _A really annoying, big, and triangular-shaped cat._

"Awe come on Pine Tree!" Bill chirped, "What kind of guardian would I be if I left you all on your lonesome!" He then waggled a finger at Dipper, tssking disapprovingly. "Just disappearing into the big, scary woods without even telling your sister! Shooting Star's gaining grey hairs as we speak! Ah! But I suppose…" Bill appeared right behind Dipper, tucking the pencil behind the boy's ear. " **You're not afraid are you?** "

Dipper yelped and swatted at him, only to fall off the stump, face flushing when Bill's cackles filled the clearing.

"Cut it out!" he snapped, losing his patience. "I know you wouldn't stalk me just because Mabel's worried! Why did you really follow me?"

Bill only hummed thoughtfully, tapping long fingers against his cane.

"Weeelll I _did_ follow you because the Tadpole was practically shoving me out of the doorway, but I mostly just came to see your lame stabs at magic!" As Dipper fumed, Bill chuckled maddeningly. "And boy do you suck! You can't even organize a basic rune properly!"

Clenching his hands tightly to avoid murdering Bill (because he and Mabel were _sweater buddies_ whatever that meant) the boy kicked aside the remains of his sketchbook, and stalked out of the clearing. Bill, unfortunately, followed, his gliding steps seemed to shorten the distance, chattering happily all the while.

"You know you could use? The Journal. I bet that baby's chock full of magic! And if you're _really_ desperate then I suppose you could ask the Tadpole, Ye Olde Magick Try-Hard. But then Pine Tree, I suppose you already knew that…" Dipper did not even glance at him. "…Oooh! Someone's got _pride issues!_ And it's not the roadkill you're about to plant your foot in."

The boy glanced down out the dead squirrel he had almost tread on, queasily taking a step over it before continuing his silent trek to the Mystery Shack. The demon seemed to pout and he lazily circled around the dead animal, poking it with his cane.

Suddenly, his eye flashed red and with a snap of his fingers, Bill incinerated the roadkill in a scorching, bright blue flame. Dipper found it particularly difficult to swallow the urge to vomit when Bill rejoined him, waving a charred piece of squirrel. "Want some? _Admit it_ , you want some!"

Winkling his nose at the smell of burnt flesh, Dipper began speed walking through the forest. The Mystery Shack was quickly gaining an appeal similar to heaven.

Undaunted, Bill tossed the squirrel's leg and glided noiselessly next to Dipper. "You know what you need?"

 _Some peace and quiet?_

"A magic teacher! Not someone _bo-ring_ square like Tadpole but someone who deals the legit goods, the juicy stuff, the Pitt in the Pitt Cola!"

Dipper grunted, carefully picking his way around a nasty patch of stinging nettle. _Ignore him. Ignore him._

"You knoooow," Bill drawled, shifting the patch of nettle a few feet to the left with a flick of the wrist. "It actually takes a lot of concentration to be able to burn a corpse without lighting the whole forest on fire. Real savvy hijinks, you catch my drift?"

Dipper was thinking about the can of bug repellent he was always carrying and _wouldn't it be nice if it worked on Bills too? Just one clean shot to the eye…_

"'Course you could never be quite as talented as _me_! But even Shooting Star's pig could learn magic if it had _me_ as a teacher!"

Forget murdering Bill. Dipper would kill himself if he had to hear more of that nasally, high pitched, drawl. Just when he was considering telling the demon to go back where he came from, the sweet _sweet_ sight of one of the Mystery Shack's many gables, peaking through the forest. The run-down tourist trap seemed to take on a divine glow.

"Sooo whaddya say!" Bill finished grandly. "Limited offer just for you Pine Tree!"

His generosity was answered by the brown-haired boy sprinting to the rickety shack and slamming the door in his face.

Dipper sighed in relief and wearily trudged towards the kitchen for a chilled Pitt Cola, ignoring Bill's indignant yells. He stubbornly muted out the persistent nudging in his head. Pity there wasn't an on/off switch for the dumb link.

The demon, meanwhile phased his way through the door, feeling very miffed. The nerve of that kid! Disregarding his amazing offer _and_ locking him out! Not that he could be locked out but still! It's the thought that counts!

Just then, Shooting Star's excited squeal filled the house, followed by Pine Tree's yelp. After that sort of behavior, Bill had half a mind to leave Pine Tree at his twin's mercy. _Let the kid get man-handled. It increases character!_

Nevertheless, he found himself floating towards the kitchen. Bill rolled his eye at the loud crashes and Pine Tree's hysterical protests. _Well at least this job keeps me on point._

He couldn't resist giggling.

 _Heh. On point._

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 **A/N: So far I have no plot in mind so just expect some snippets. :P Please R &R! **


	2. Prologue: END

**A/N: Whoo! Finally got this out of my system! Bill and CO. will be much, much, much more compassionate and kind for reasons explained later. Also: failed feels. Thank You so much for checking this out and giving it a chance! A _Twenty-Fifth Last_ CHANCE.**

 **No? Well alright then. Read on!**

 **Disclaimer:Alex Hirsch (and Disney) own Gravity Falls. And my heart. starfleetrambo. tumblr is a fount of inspiration.**

* * *

 _The Legacy of Duck-Tective: The Freakishly Freezing Freezer_ was a lot less interesting than it had seemed on TV. Dipper was almost impressed by how this book managed to simultaneously bore him and confuse him. The present situation was also somewhat distracting.

Mabel had been as hyper and touchy as ever when he had returned, lifting him up around his waist and twirling him, laughing with relief, threatening to make him dizzy unless she told him exactly why he had thought he could escape her grasp. No matter how close they were, the reason behind Dipper's impromptu frolic into the woods was one thing Mabel couldn't know. So, he had mumbled a lame excuse while glaring at the silently laughing Bill in the corner. To his surprise, Mabel hadn't protested but had only stared at him silently before nodding silently.

Being the pre-teen introvert he was, Dipper appreciated and thrived in silence. However, his twin's ritual of muteness was outright disturbing and worrisome. The atmosphere was heavy, the absence of Mabel's cheerful chatter looming over him like a dark cloud. The fact that Dipper knew the exact, and perfectly reasonable reason, for Mabel's behavior, was no help.

The boy glanced up from the book he was pretending to read, peering cautiously over at his twin's bed. It was a rather discouraging sight.

Silent anger seemed strange on Mabel, with a thick, curly mane of brown hair and rosy, freckled face that had not quite lost all its baby fat. Unlike Dipper who was all angles, Mabel was curvier and bulges of muscle (souvenirs from boxing with Gunkle Stan) only filled her form.

Mabel's lips were pursed tightly as she lay on her stomach, on top of a complacent Waddles (or he was sleeping) (Dipper could never really tell), diligently knitting at the speed of light. If Dipper looked hard enough, he could even catch the sparks of hot-pink magic dancing along the needles. Not once, did she look up.

After several more minutes of stagnant silence, Dipper decided to grab the bull by the horns. Palms already becoming slick, he cleared his throat. The resulting sound was something like a dying goat's mating call.

Waddles let out a loud snort but Mabel only increased her knitting speed, needles flashing in a blur, a consistent clack filling the attic.

"So… what are you making?" Dipper ventured. Silent Mabel was much, much more intimidating than Teasing Mabel. _Even if her punches did hurt._

Clickity-Clack. Mabel mutely finished another row, tugging at the ball of rainbow yarn.

"Heh…heh. That's uh, real nice." the boy chuckled weakly, retreating to his book. Mentally, he raged in frustration and embarrassment. _I…am not a people person._

He usually just left the talking to Mabel. Mabel, who was very unlike to be of help now. But Dipper wasn't known for giving up (whether this trait was a blessing or a burden was up to debate).

"So…you can uh do magic. Magical things," he continued, forcing away the urge to chew something to tatters. "Magical things with sweaters. That's a sweater right?"

When his twin abruptly paused at her knitting and gazed at him with a blank expression, Dipper flustered and hurriedly corrected himself. "Not that I'm discriminating! Because, that would be sweater-cist. I'm sure that's a very nice…rug…with holes. They could be like…mini-cup holders. For your feet."

Wordlessly, Mabel returned to her work, expertly tying and snipping the yarn, shaking out and inspecting the shapeless, rainbow blob with holes. Dipper's heart sank to the bottom of his stomach. "Right. Sorry." The weight of guilt, which re-settled on his shoulders, seemed to be twice as heavy. With a sting, Dipper remembered just how many times he had yelled or nagged Mabel to be quieter. _Ask and you shall receive huh…_

He almost jumped out of his bed when Mabel tossed the woolen shape at him and said quietly, "It's a sweater vest. A sweater vest for a dumb brother who won't stay out of trouble."

Dipper swallowed and said, "Mabel I-"

Mabel continued, growing louder. "It's super colorful so I can find him in any creepy forest. It'll keep him warm until he can build a fire. It's super magical so that no matter how dumb he is, he won't get hurt." She finally faced him, lower lip trembling. "It'll also remind him that, no matter what, I love him…5ever."

She wiped hastily at her eyes before ducking out of sight, pulling the quilt around her and Waddles. Loud snores soon erupted from Mabel's side of the room, leaving Dipper staring at the sweater vest in his hands. His mouth opened-and closed with a clack of teeth. In the end, Dipper carefully folded the sweater and gently laid it aside. He then switched off his lamp and curled underneath the covers.

Mabel's loud snores gradually subsided until they disappeared as she believed him to be asleep. The twins lay in their beds, listening to the frogs croak, the crickets chirp, and the leaves rustle in a warm breeze.

Eyes slowly adjusting to the velvety darkness, Dipper took a deep breath before murmuring with pretend drowsiness. "Hey Mabel…Want to go exploring tomorrow? Together?"

Mabel's breathing stopped short and Dipper cringed at what was coming next. A long pause. But instead of a biting remark, only a quiet, "Sure Bro bro" floated over.

Dipper's face split into a smile, but he managed a nonchalant, "Cool. G'night". And so, the two twins (and a pig) drifted off into sleep, with faint smiles on their faces.

Bill leaned against the mossy, cracked roof tiles idly teleporting fireflies, ignoring the blubbering demon next to him. He lost control when Tad leaned his square head against his shoulder, glowing tears seeping through his jacket.

"Alright! I know you want to do your part for the water cycle but the last thing we need is another flood!" Bill said haughtily, disdainfully pulling the square demon from his damp, glowing shoulder. "Okaaay. You are _not_ dribbling your astral fluids on _this_ suit. Erminegildo Zigna Bespike is difficult to steal!"

Patting himself down for a handkerchief and finding none, Bill pulled up a nearby wad of moss, shook of the bugs, and handed it to Tad. The square demon gratefully accepted the moss, pressing it to his flowing eye. As soon as the moss soaked up the glowing tears, they exploded into bright blue flames. Tad brushed off the flecks of ash from his dark navy butler uniform, his sniffles settling down.

Bill retrieved Tad's discarded, black bowler hat, patting the other demon on the shoulder awkwardly. "Hey hey," he said. "You good?" Tad breathed deeply and blinked the last of his tears away, posture immediately snapping straight.

"Of course," he said coolly dignified, as if he had not been sobbing moments earlier. "You must excuse my earlier episode. I was merely moved by Lady Mayabella's interaction with her brother. Most touching."

This of course, translated to: 'Tell anyone and I'll glue your top hat to your head'. Bill rolled his eye, kicking his long legs along the side of the ledge. Tad, however, was not finished.

"Lady Mayabella is progressing marvelously with her studies", he said. "Today, she created several likenesses of her family out of that strange substance she calls…Fun-Dough, solely using her mind. A regular prodigy one might say."

Bill grunted and teleported a whole crowd of fireflies. Tad looked at him expectantly.

"I get it I get it," Bill grumbled at last. "My kid's brilliant too. That head of his could pack all the spells in the world. 'Course it's expected, being my kid after all. But he's got five issues for every drop of potential. How am I supposed to teach a kid who can't even trust himself?"

"Do you trust him?" Tad asked somberly. Bill rolled his eyes in a 'No Duh' manner. "Does he know that?" All the sassiness drained from the triangular demon. He slumped slightly. Tad nodded sympathetically.

"These kids…" Bill groaned. "Are _nothing_ like their ancestors." He sighed and took off his top hat, fiddling with the edges. "I made him the most obvious offer in the history of obvious offers, no strings attached. Since when do I do that?" He looked at Tad who nodded again, before throwing his hands into the air. "I don't know Tadpole. I don't know. Maybe it wasn't a good idea to contract kids."

The sounds of wildlife dominated the clearing once again.

"Well," Tad said quietly. "I think we made the right choice. And I think you're doing fine." Bill only nodded mutely. Humming in thought, Tad tapped a slender, white-gloved finger against the dirty roof-tile. "Perhaps…," the triangle demon mused. "We should acompany them on their outing…Who knows? That journal of theirs is horridly abridged. They might find need of a reliable source on the matters of magic. Or two."

Bill literally brightened up, emitting soft, gold glow that caused a few stray moths to flutter near. "Tadpole," he said slowly. "I think I have the _perfect_ destination."

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 **A/N: Reviews give me joy! And for your deciphering pleasure~ MVCG GRNV: Z SLOV MVD DLIOW**


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